Highlight likely propagation duct, improve contact detail layout

- Mark duct closest to endpoint elevations as likely signal path
- Likely duct drawn with solid borders, bold label, stronger fill
- Other ducts shown dimmed with dashed borders
- Fix path info layout: table columns prevent El wrapping
- Surface observations as compact table, limited to 5 nearest stations

assets/js/elevation_profile_hook.js

@@ -22,12 +22,17 @@ const ductPlugin = {
       const drawBase = Math.min(yBase, bottom)
       if (drawTop >= drawBase) continue
 
-      ctx.fillStyle = "rgba(34, 197, 94, 0.12)"
+      const likely = duct.likely
+      const fillAlpha = likely ? 0.18 : 0.08
+      const strokeAlpha = likely ? 0.8 : 0.3
+      const lineWidth = likely ? 1.5 : 1
+
+      ctx.fillStyle = `rgba(34, 197, 94, ${fillAlpha})`
       ctx.fillRect(left, drawTop, right - left, drawBase - drawTop)
 
-      ctx.strokeStyle = "rgba(34, 197, 94, 0.5)"
-      ctx.lineWidth = 1
-      ctx.setLineDash([4, 3])
+      ctx.strokeStyle = `rgba(34, 197, 94, ${strokeAlpha})`
+      ctx.lineWidth = lineWidth
+      ctx.setLineDash(likely ? [] : [4, 3])
       ctx.beginPath()
       ctx.moveTo(left, drawTop)
       ctx.lineTo(right, drawTop)
@@ -38,13 +43,15 @@ const ductPlugin = {
 
       // Label
       const labelY = Math.max(drawTop + 12, top + 12)
-      ctx.fillStyle = "rgba(34, 197, 94, 0.8)"
-      ctx.font = "9px sans-serif"
+      const textAlpha = likely ? 1.0 : 0.5
+      ctx.fillStyle = `rgba(34, 197, 94, ${textAlpha})`
+      ctx.font = likely ? "bold 10px sans-serif" : "9px sans-serif"
       const labels = {hrrr: "Duct", sounding: "Duct (sounding)", inferred: "Est. duct"}
       const units = {hrrr: "M-units", sounding: "M-units", inferred: "dN/dh÷10"}
       const prefix = labels[duct.source] || "Duct"
       const unit = units[duct.source] || "M-units"
-      ctx.fillText(`${prefix} ${Math.round(duct.base_ft)}–${Math.round(duct.top_ft)} ft (${duct.strength} ${unit})`, left + 4, labelY)
+      const tag = likely ? " — likely path" : ""
+      ctx.fillText(`${prefix} ${Math.round(duct.base_ft)}–${Math.round(duct.top_ft)} ft (${duct.strength} ${unit})${tag}`, left + 4, labelY)
     }
     ctx.restore()
   }
@@ -69,7 +76,8 @@ export const ElevationProfile = {
       base_ft: d.base_m_msl * M2FT,
       top_ft: d.top_m_msl * M2FT,
       strength: d.strength,
-      source: d.source || "hrrr"
+      source: d.source || "hrrr",
+      likely: d.likely || false
     }))
 
     const allElevs = [...elevations, ...losLine]

lib/microwaveprop_web/live/contact_live/show.ex

@@ -257,18 +257,18 @@ defmodule MicrowavepropWeb.ContactLive.Show do
             {format_band_ghz(@contact.band)} · {@contact.mode}
             · {format_dist(@elevation_profile.dist_km)}
           </div>
-          <div class="grid grid-cols-2 gap-x-8 text-sm font-mono mb-2">
-            <div>
-              {@contact.station1} &rarr; {@contact.station2}
-              <span class="ml-4">Az: {format_bearing(@elevation_profile.fwd_az)}</span>
-              <span class="ml-4">El: {@elevation_profile.fwd_el}&deg;</span>
-            </div>
-            <div>
-              {@contact.station2} &rarr; {@contact.station1}
-              <span class="ml-4">Az: {format_bearing(@elevation_profile.rev_az)}</span>
-              <span class="ml-4">El: {@elevation_profile.rev_el}&deg;</span>
-            </div>
-          </div>
+          <table class="text-sm font-mono mb-2 mx-auto">
+            <tr>
+              <td class="pr-6">{@contact.station1} &rarr; {@contact.station2}</td>
+              <td class="pr-6">Az: {format_bearing(@elevation_profile.fwd_az)}</td>
+              <td>El: {@elevation_profile.fwd_el}&deg;</td>
+            </tr>
+            <tr>
+              <td class="pr-6">{@contact.station2} &rarr; {@contact.station1}</td>
+              <td class="pr-6">Az: {format_bearing(@elevation_profile.rev_az)}</td>
+              <td>El: {@elevation_profile.rev_el}&deg;</td>
+            </tr>
+          </table>
 
           <%= if @elevation_profile.verdict == "BLOCKED" && @elevation_profile.first_obstruction_km do %>
             <div class="bg-error/10 text-error font-semibold px-3 py-1 rounded mb-2 text-sm">
@@ -645,6 +645,7 @@ defmodule MicrowavepropWeb.ContactLive.Show do
         |> merge_nearby_ducts()
         |> Enum.sort_by(& &1.strength, :desc)
         |> Enum.take(3)
+        |> mark_likely_duct(tx_elev, rx_elev)
 
       %{
         points:
@@ -785,6 +786,32 @@ defmodule MicrowavepropWeb.ContactLive.Show do
     |> Enum.reverse()
   end
 
+  # Mark the duct most likely carrying the signal. The signal enters at
+  # surface level from each end, so the duct whose base is closest to
+  # the average endpoint elevation is the most probable propagation path.
+  defp mark_likely_duct([], _tx_elev, _rx_elev), do: []
+
+  defp mark_likely_duct(ducts, tx_elev, rx_elev) do
+    avg_elev = (tx_elev + rx_elev) / 2
+
+    {likely_idx, _} =
+      ducts
+      |> Enum.with_index()
+      |> Enum.min_by(fn {d, _idx} ->
+        # Distance from average endpoint elevation to the duct layer
+        # Prefer ducts that the endpoints are actually inside of
+        if avg_elev >= d.base_m_msl and avg_elev <= d.top_m_msl do
+          -d.strength
+        else
+          min(abs(d.base_m_msl - avg_elev), abs(d.top_m_msl - avg_elev))
+        end
+      end)
+
+    Enum.with_index(ducts, fn d, i ->
+      Map.put(d, :likely, i == likely_idx)
+    end)
+  end
+
   defp band_to_ghz(nil), do: 10.0
 
   defp band_to_ghz(band) do